One of Britain's most eccentric museums, a treasure trove of cinema nostalgia collected by one man over 60 years, is facing closure after being told to vacate its premises in six months.

The Ronald Grant Cinema Museum is an Aladdin's cave of ashtrays, carpets, chandeliers, curtains, 'house full' signs, light fittings, popcorn cartons, projectors, tickets and ushers' uniforms from cinemas demolished long ago. It also boasts a colossal archive of books, films, financial accounts, magazines, sheet music and around a million photographs crammed from floor to ceiling. The walls are adorned with posters for classic movies such as Mutiny on the Bounty and The Smallest Show on Earth.

Grant, now 71, fell in love with film as a boy, helping the manager of his village cinema in Banchory near Aberdeen, and has spent a lifetime amassing the collection. It is housed in Lambeth, south London, in a former workhouse built in 1871 where Charlie Chaplin stayed as a child, and which became part of Lambeth Hospital in 1920.

Now the building's owner, the South London and Maudsley NHS Trust, has terminated the museum's tenancy so that it can sell the entire complex, estimated at more than 1,500 square metres. The museum is appealing for benefactors to help it find a new home by the March deadline.

'It's mindblowing that we don't have anywhere to move to,' said Martin Humphries, the museum's co-director. 'We've put out feelers to see if we can find somewhere. It's a headache because we want to move in as economic a way as possible, but the size and fragile nature of the collection means we can't pay a professional company to do it in its entirety.

'Not knowing where we'll be in six months' time is depressing. The ideal would be somewhere more accessible than now, but if it's smaller then the collection might have to be broken up and dispersed to like-minded people. If we can't find anywhere suitable, we'll have to close. It would be wonderful if there was someone out there with a love of cinema who would like to offer help and support.'

Humphries added that he did not blame the NHS trust for ordering the move. 'They've done what they're expected to do: rationalise their assets. The building is no longer suitable for NHS use. The knock-on effect is that we're homeless. The NHS trust is not being difficult, but if we haven't found somewhere and they insist on us moving out, it might look different.'

The move could work to the cramped museum's advantage if it finds a more prominent and user-friendly location. It is currently one of London's best-kept secrets, tucked away in a quiet cul-de-sac well off the tourist trail, and visits are by appointment only. It is popular with historians and researchers, and generates revenue by syndicating pictures from its vast library to newspapers and magazines. Its patrons include film director Ken Loach and Labour MP Gerald Kaufman.

The tightly packed exhibits include a Kalee film projector from the Thirties, stacks of the Kine Weekly film magazine, wooden category boards which used an 'H' to signify a horror film and some original negatives shot by Sagar Mitchell and James Kenyon, whose footage of everyday life in late Victorian and early Edwardian Britain was rediscovered in 2002 and became a hit for the BBC. There is even a rare print of a film by the British director Michael Powell lying in storage. Among Grant's favourite possessions is an ashtray made for a 1931 Sherlock Holmes film, an accounts book showing that a cinema pianist was drunk and had to be replaced, and the original negative of an 1896 film entitled A Victorian Lady in Her Boudoir in which an actress performs a striptease.

Richard Morley, spokesman for the NHS Trust, said: 'The building is very old with a high upkeep cost. The plan is to sell off the building and put the money back into the trust as part of the state strategy looking to rationalise services.'